This almost makes me want to get my lazy butt out of bed early one morning and go take some photographs!
It is interesting that you shot it square (probably) and then cropped it and I kind of see it as a square more or less. The top of the image is superfluous to me since the interest lies in the contrast between the calm water and the movement in the sky. Feel free to ignore this comment.
Thank you all for the comments. Patrick, I guess it just looked better to me as a vertical - the print shows some more detail in the top part of the sky than what came through in the scan. But, you've got me thinking, and I'm going to take a look at it again tonight when I get home. Bill, we'll probably be getting up north again sometime in the winter. I'll let you know. -Mark